Coking coal



Patented Apr. 1, 1952 COKING COAL Ernst Berl, deceased, late of Pittsburgh, Pa., by Walter G. Berl, executor, Pittsburgh, Pa.

No Drawing. Application August 6, 1946, Serial N0. 688,682

Claims.

The present invention relates to a process of converting a non-coking carbonaceous material into a good, dense coke and to the product thereof containing only a few tenths of a percent of ash and practically no sulfur.

Heretoiore, only true bituminous coals upon coking produced dense and hard coke suitable for blast furnaces and foundries. Wood, peat, lignites, sub-bituminous coals, semi-anthracites and anthracites upon coking, especially at normal pressure, give either sandy coke or sintered coke with little if any mechanical strength.

There exist large deposits of these non-coking coals not only in this country but in many other parts of the World. It is of great importance to convert these non-coking coals, which like the lignites in the Dakotas, Utah and Wyoming can be produced at very low cost, into coking coals. The already used method of adding small portions of these non-coking fuels to those bituminous coals which alone upon coking form a very porous coke is not the ideal solution of this important problem.

Many other propositions have been made to solve this task. One has added binders, for instance waste sulfite liquor. For different reasons these processes have not contributed very much to the solution of the problem of converting large deposits of non-coking coals into coking coals.

The quantity and quality of what is called bitumen in those fuels are the reasons for the noncoking properties of wood, peat, lignites, subbituminous coals, semi-anthracites and anthracites. Bitumen is generally considered as that part of natural or artificial coals which can be extracted with appropriate solvents. Polar s01- vents, especially ketones, at elevated temperature and, if necessary, pressures, for instance acetone (B. P. 565 0.), acetophenone (B. P. 202.3 C.), benzophenone (B. P. 306 C.), furthermore su stances like tetrahydronaphthalene (B. P. 206 C.) are the best solvents for bitumen. Phenols and amino compounds like aniline and homologues may be used for the same purpose. Extended studies have shown that natural and artificial coals, the latter produced from carbohydrates or carbohydrate-containing materials, contain enough bitumen with the necessary qualitative properties to yield those hard cokes which are needed in blast furnaces and foundries. It has been found that the bitumen in natural coking coals and in coking artificial bituminous coals at the high coking temperature of 800-1000" C. forms gases and vapors like CO2, steam, methane, benacne. and homologues. The high melting decomposition products at the high coking temperature cement together the non-coking residual coal par ticles which are insoluble in the aforementioned or other solvents. The coal substance at elevated temperature goes through one or several plastic stages. Porous coke results if the formation of gases and vapors occurs when the coal substance is plastic. Dense coke results if this development occurs before or after the-plastic stage has been reached. f

The reason that wood, peat, lignites, subbituminous coals, semi-anthracites and anthracites do not form dense, coherent coke has been found to be either in the lack of a suflicient amount of bitumen, or in its unfavorable properties, or both. Certain bitumens which may be present in suiiicient quantities in natural or artificial coals distill away upon coking before they have been cracked under formation of those already mentioned high melting substances which cement insoluble residual coal particles together. Finally, these bitumen conversion products are completely cracked under formation of secondary carbon.

It is an object of the invention to provide a process of coalifying non-coking coals with materials rich in carbohydrates in presence of alkali to produce an excellent coking coal.

The invention also contemplates the provision of a process of converting non-coking coal into a dense or porous coherent coke by intimately mixing with a non-coking coal a conversion product of carbohydrate-containing material obtained at an elevated temperature in the presence of alkali and then coking the mixture at coking temperatures.

It is also an object of the invention to provide a process for the coalification of lower rank coals with a conversion product obtained from carbohydrates or carbohydrate-containing material in the presence of an alkali at a high temperature whereby a non-coking coal can be converted into a coking coal capable of being converted into a good coke.

Moreover, it is likewise within the contemplation of the invention to provide a process of converting non-coking coals into coking coals by adding thereto artificially converted carbohydrates or bitumens or high boiling phenolic and phenolic carbonic compounds obtained from such carbohydrates.

A further object of the invention is a substantially sulfur-free 'coke containing less than 1% of ash.

Other objects and advantages of the invention 3 will become apparent from the following description.

Broadly stated, the present invention comprises the important fact that by combining the coalification of lower rank coals, for instance peat or lignites, with conversion of carbohydrates or carbohydrate-containing material. in alkaline medium, one can getirom the otherwise non-coking coals which always give sandy coke a good coke which can also be used for these most important metallurgical operations. One can get these same results with more expensive anthracite coals but this is much less important than the conversion of peat or lignites into coking coals.

One can get conversion of non-coking coals into coking coals by adding either the bitumen of these artificially converted carbohydrates, or better its high boiling phenolic and phenol carbonic compounds. It was found that bitumen from coking coals can be obtained with rather high yields by thetreatrnent with polar substances, for instance ketones, or phenols, or amino compounds like aniline After separation of the bitumen from the extracting agents, this bitumen when added in suflicient. quantities to these non-coking coals in such a way that a uniform distribution takes place converts the non-coking material into excellent coking coal.

In particular, the invention contemplates several methods. One method consists in mixing with non cokingcoals material rich in carbohydrates and adding to this system suiiicient amounts of alkaline-reacting substances like lime, limestone, dolomite, magnesite, sodium hydroxide,sodium sulfide, sodium'carbonate, ammonium hydroxide, ammonium hydrosulfide, iron carbonate, iron sulfide,- iron hydroxide, etc. This mixture ofnon-coking coalsplus materials rich in carbohydrates plus alkali in presence of water or liquidpolar alcohols like glycol or glycerine, or mineral oil is subjected 'to higher temperature up to 30 0-450 C. in a closedvessel or a pipe still with pressure reduction valve so that otherwise volatile-substances cannot escape at lower temper-atures. As plant material to be added any carbohydratecontaining material like sawdust, leaves, grass, rotten grain, cornstalks, cotton, seaweed, algae, sugar cane, bagasse, Irish moss, starch-containing material like potatoes, etc. may be, used. .Theso-calledffblack liquor from the sulfide 'pulp production due to its sugar content can be used also for the same purposes.

3 When this mixture is exposed to higher temperature; several important processes take place. The carbon content of, for instance, peat or lignite plus added organic material increases from around 45-60% up .to 78-85%. This is due to an intramolecular reaction. Withthe loss of carbon dioxide, methane and water, the carbohydrates .under the influence of alkali are converted into material relatively high in carbon. Th lignin part of the coals and of the added plant material increases the amount of non-coking residual coal. The carbohydrate content of the aforementioned materials under the influence of alkali is converted into enough bitumen having the right properties and upon coking being converted into high melting, less volatile substances which cement the residual coal particles together. They are finally converted into secondary carbon.

, The amount of plant material and alkali to be added to non-coking natural coals depends on the composition of the latter. Only small amountsof plant materialhave to be added to peat which is rich in carbohydrates. Larger amounts of carbohydrate-containing plant material have to be mixed with lignites which have different compositions. Certain lignites are mostly derivatives of lignin. They contain lignin humic acids which in themselves have no coking properties. Other lignites contain larger amounts of carbohydrate humic acids. Those lignites need less additional carbohydrate-containing plant material and alkali than the former class of lignites.

Subbituminous coal may have derived to a large extent from carbohydrate-containing plant materials. Due to geochemical conditions during their formation, bitumen has been formed from the carbohydrates which on account of its volatile properties distills away nearly unde= composed when the coals are subjected to higher temperature. If treated under pressure at elevated temperature in closed vessels those subbituminous coals need relatively little additional carbohydrate-containing plant material plus alkali. The bitumen already present with this treatment at elevated temperature is changed in such a way that it becomes less volatile. The newly formed carbohydrate bitumen plus the changed original bitumen are now present in suiiicient quantities with the desired qualities so that excellent coking coal results.

Semi-anthracites and anthracites may have been formed from carbohydrate-containing material, but also from lignite derivatives. They contain not enough bitumen to beused as coking coals. Those anthracite coals need larger quantities of carbohydrate-containing material plus alkali so that upon treatment in a closed vessel in presence of water and temperatures below or above the critical temperature of water sufficient bitumen of the right quality together with non-coking residual coal are formed.

For the purpose of giving those skilled in the art a better understanding of the invention, the following illustrative examples will now be described.

Emample 1 Peat (48-60 C content) is suspended in water which contains alkali in form of suspended limestone, dissolved and suspended lime, dolomite or sodium hydroxide. The ratio of suspended or dissolved alkali to dry peat should be about 1-5 parts of alkali (calculated as NaOH) to 100 parts of dry peat. The higher alkali amount may be used when older peat has to be converted, ,the lower figure is for younger peat. The mixture either in a pipe still or by a batch operation-is brought up to 325-350 C. (620-660 F.) and'kept at this elevated temperature for a longer or shorter time. The reaction product is finely powdered black coal with 78-82% C content. It can be pressed to larger pieces atelevated temperature (IOU-200 C.) and higher pressure. 'Upon coking the former non-coking peat yields excellent dense coke.

Example 2 Sawdust with alkalized waterira tio of wood substance to NaOH or its equivalent 10051-3) are treated as described in Example 1. 'C'okihg coal with l0-45% yield based on dry sawdust'is obtained. A few tenths of one percent crash content and no sulfur are present. This compares with up to 12% of ash and up to 5% of sulfur in natural coking bituminous coals. Less than 50% (based 'on the weight oi'fthe original sawdust) of a dense coke results upon coking at 800-1000 C. This material,. due to its low .ash content, can be used for electrodes.

Example 3 Lignites with little content in" cellulose-humic acids are intimately mixed with 10-100% of their weight with carbohydrate containing wastes, for example, sawdust, seaweed, algae. bagasse, cornstalks, etc. The ratio of added material to alkali (calculated as 100% NaOH) may be 100:2-25. After treatment as described in Example 1, an excellent coking coal with total yields between 61 and 52% result.

Example 4 Example 5 The so-called black liquor which results as a byproduct from the sulfide pulp production contains, besides not very well defined acid lignin derivatives in form of their water soluble alkali salts, a rather large amount of carbohydrates resulting from the hydrolysis of hemicelluloses and other carbohydrates contained in wood. This black liquor is mixed directly with noncoking coal, brought to dryness and incoalified in a closed vessel at temperatures up to 370 C. After cooling down a coal results which gives a coherent dense coke.

If one adds somewhat more alkali to the waste black liquor, the greatest part of the lignin derivatives are converted into coal whereas the carbohydrates are converted into a viscous asphalt-like material.

The invention is not limited to the foregoing examples or to any specific data given in the foregoing description. Modifications and equivalents within the spirit of the present invention will be readily apparent to the expert and are therefore comprised within its scope. It is therefore intended to claim the invention broadly, and to be limited only by the appended claims.

What is claimed is:

1. Process of making a mechanically strong coke from non-coking coal, comprising heating in a closed system a non-coking coal in an alkaline liquid medium and in the presence of a carbohydrate-containing material, the alkalinity of said liquid medium being that of at least 2 parts by weight, calculated as NaOH, per 100 parts by weight of said carbohydrate-containing material, at a temperature above the temperature at which said medium boils at atmospheric pressure, whereby a superatmospheric pressure results in said closed system, until said carbohydratecontaining material is transformed into a bituminous substance characterized by phenolic groups and a composition of coal and said bituminous substance is formed, and subjecting said composition to a coking temperature of the order of at least 800 0. whereby said phenolicgroups-containing bituminous substance is decomposed at said coking temperature and the non-volatile residue therefrom cements said coal.

2. Processof making a mechanically strong coke from non-coking coal, comprising heating in a closed system a non-coking coal in an alkaline liquid medium and in the presence of a carbohydrate-containing material, the alkalinity of said liquid medium being that of at least 2 parts by weight, calculated as NaOI-I, per parts by weight of said carbohydrate-containing material, at a temperature between about 300 C. and about 450 0., until said carbohydratecontaining' material is transformed into a bituminous substance characterized by phenolic groups and a composition of coal and said bituminous substance is formed, and subjecting said composition to a coking temperature of the order of at least 800C whereby said phenolicgroups-containing bituminous substance is decomposed at said coking temperature and the non-volatile residue therefrom cements said coal.

3. Process of making a coking coal, comprising heating in a closed system a substantially noncoking coal in the presence of a carbohydratecontaining material in a liquid alkaline medium whose alkalinity is that of at least 2 parts by weight, calculated as NaOH, per 100 parts by weight of said carbohydrate-containing material, at a temperature above the temperature at which said liquid medium boils at atmospheric pressure, whereby a superatmospheric pressure results in said closed system, until said carbohydrate-containing material is transformed into a bituminous substance characterized by phenolic groups and a composition of coal and said bituminous substance is formed; said composition being convertible at a coking temperature of the order of at least about 800 G. into a mechanically strong coke cemented together by the residue from the decomposition of said phenolicgroups-containing bituminous substance at said coking temperature.

4. Process of making a coking coal, comprising heating in a closed system a substantially noncoking coal in the presence of a carbohydratecontaining material and in a liquid alkaline medium whose alkalinity is that of at least 2 parts by weight, calculated as NaOH, per 100 parts by weight of said carbohydrate-containing material, at a temperature between 300 C. and 450 C., until said carbohydrate-containing material is transformed into a bituminous substance characterized by phenolic groups and a composition of coal and said bituminous substance is formed; said composition being convertible at coking temperatures of the order of at least 300 G. into a mechanically strong coke cemented together by the residue from the decomposition of said phenolic-groups-containing substance at said coking temperature.

5. The process according to claim 3, wherein said carbohydrate-containing material is wood.

6. The process according to claim 3, wherein said carbohydrate-containing material in said alkaline liquid medium is black liquor of the type obtained in sulfide wood pulp production.

7. The process according to claim 3, wherein said carbohydrate-containing material is seaweed.

8. The process according to claim 3, wherein said carbohydrate-containing material is bagasse.

9. The process according to claim 1, wherein said non-coking coal starting material is anthracite.

10. The process according to claim 3, wherein said iibn-coking bai starting material is anthracite.

WALTER G. BERL, Executor of the Last Will and Testament of Ernst Berl, Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

Number 1 n umber Name Date Summers Mar. 9, 1926 Johnston et a1 Jan. 10, 1928 Erlenbach June 17, 1930 Little June 9,1931 Poi/t July 18, 1939 Otto Aug. 14, 1945 FOREIGN PATENTS Country Date Great Britain Dec. 22. 192'? Great; Britain Oct.- 16, 1934 Great Britain Nov. 53.1935 Great Britain Jan. 24, 1939 

1. PROCESS OF MAKING A MECHANICALLY STRONG COKE FROM NON-COKING COAL, COMPRISING HEATING IN A CLOSED SYSTEM A NON-COKING COAL IN AN ALKALINE LIQUID MEDIUM AND IN THE PRESENCE OF A CARBOHYDRATE-CONTAINING MATERIAL, THE ALKALINITY OF SAID LIQUID MEDIUM BEING THAT OF AT LEAST 2 PARTS BY WEIGHT, CALCULATED AS NAOH, PER 100 PARTS BY WEIGHT OF SAID CARBOHYDRATE-CONTAINING MATERIAL, AT A TEMPERATURE ABOVE THE TEMPERATURE AT WHICH SAID MEDIUM BOILS AT ATMOSPHERIC PRESSURE, WHEREBY A SUPERATMOSPHERIC PRESSURE RESULTS IN SAID CLOSED SYSTEM, UNTIL SAID CARBOHYDRATECONTAINING MATERIAL IS TRANSFORMED INTO A BITUMINOUS SUBSTANCE CHARACTERIZED BY PHENOLIC GROUPS AND A COMPOSITION OF COAL AND SAID BITUMINOUS SUBSTANCE IS FORMED, AND SUBJECTING SAID COMPOSITION TO A COKING TEMPERATURE OF THE ORDER OF AT LEAST 800* C. WHEREBY SAID PHENOLICGROUPS-CONTAINING BITUMINOUS SUBSTANCE IS DECOMPOSED AT SAID COKING TEMPERATURE AND THE NON-VOLATILE RESIDUE THEREFROM CEMENTS SAID COAL. 